In response to the demands of consumers who are driven both by ever-escalating fuel prices and the dire consequences of global warming, the automobile industry is slowly starting to embrace the need for ultra-low emission, high efficiency cars. While some within the industry are attempting to achieve these goals by engineering more efficient internal combustion engines, others are incorporating hybrid or all-electric drive trains into their vehicle line-ups. To meet consumer expectations, however, the automobile industry must not only achieve a greener drive train, but must do so while maintaining reasonable levels of performance, range, reliability, safety and cost.
In recent years there have been several incidents of a rechargeable battery pack, contained within a laptop computer or utilized in a vehicle, catching on fire. As a result, one of the primary issues impacting consumer confidence with respect to both hybrid and all-electric vehicles is the risk of a battery pack fire.
Rechargeable batteries, due to their chemistries, tend to be relatively unstable and prone to thermal runaway, an event that occurs when a battery's internal reaction rate increases to such an extent that it is generating more heat than can be withdrawn. If reaction rate and heat generation go unabated, eventually the heat generated becomes great enough to cause the battery and materials in proximity to the battery to combust. Thermal runaway may be the result of a battery short, for example a short due to a leak within an internal battery pack cooling system. Thermal runaway may also be caused by a manufacturing defect, improper cell use, exposure to extreme temperatures, or damage such as that which may be sustained during an accident or when road debris dents or punctures the battery pack.
Although the prior art discloses numerous techniques for cooling the battery pack of an electric vehicle, a thermal management system is needed that is both cost effective and capable of maintaining the batteries within their desired operating temperature range while minimizing the risks to the vehicle's passengers. The present invention provides such a system.